The invention relates to a process and an arrangement for spinning staple fibers into a yarn, in which sliver-shaped fiber material is opened up into individual fibers which are guided to a collecting surface which moves at a speed which corresponds to at least the feeding speed of the individual fibers and which conveys the fibers to a withdrawal point, the collecting surface tapering between the feeding point and the withdrawal point and, during the conveyance to the withdrawal point, bundling the fibers into a fiber composite which is withdrawn at the withdrawal point while receiving a twist.
In the case of a process and arrangement of this type, as it is known from the German Patent Document DE-A 36 24 190, a drafting of the fed fiber material takes place to the desired yarn size with an opening-up into individual fibers. The individual fibers are fed to the collecting surface in an amount which corresponds to the yarn size to be spun so that a subsequent doubling is avoided which is always connected with the danger of a tangled position of the fibers. The separated fibers are then only bundled into a fiber composite transversely with respect to the direction of the continued conveyance. In the known construction, it is provided that the bundled fiber composite, while a twist is introduced simultaneously, is withdrawn against the moving direction by which it moves on the collecting surface.
It is also known from European Patent Document EP-B 0 236 324 to double the separated fibers on a collecting surface so that the desired yarn size is obtained. The collecting surface then conveys the fiber composite to a withdrawal point at which the fiber composite is withdrawn in the direction in which it is fed while a twist is introduced at the same time. In this case, the withdrawal speed corresponds essentially to the feeding speed of the collecting surface.
It is an object of the invention to provide a process and an arrangement of the initially mentioned type by which the yarn quality is further improved by maintaining a parallel position of the fibers.
This object is achieved in that the withdrawal of the fiber composite at the withdrawal point takes place in a direction which corresponds essentially to the conveying direction of the fiber composite on the collecting surface, a withdrawal speed being provided which is essentially equal to the conveying speed of the collecting surface.
By these measures, it is ensured that the fibers, after the separation until the time of the binding into a yarn, by no means, reduce their speed abruptly, but keep it constant or rather accelerate. This achieves that abrupt reversals of movements are avoided which result in backups and tangling of the fibers. Very high yarn delivery speeds may be achieved without the requirement of drafting units for this purpose. In this case, it is advantageous for the fiber material to be fed in the form of several slivers. By means of such a multi-sliver presentation, an effective doubling effect is obtained even before the fibers are separated.
In a further development of the invention, it is provided that a running-back of the twist in the withdrawn fiber composite in the area of the withdrawal point is prevented. This results in a false-twist-spun yarn which consists of an essentially untwisted yarn core and exterior yarn ends wound around it.
In another development of the invention, it is provided that the fiber composite receives a twist which runs back beyond the withdrawal point. As a result, a yarn is obtained which has a true twist, that is, which also is twisted in the yarn core.
In a further development of the invention, it is provided in the case of an arrangement for the spinning of staple fibers into a yarn which has a feeding and opening device which opens up sliver-shaped fiber material into individual fibers, a collecting device which follows and moves essentially in the feeding direction of the individual fibers and which has a collecting surface tapering from a feeding point to a withdrawal point, a withdrawal device which follows the withdrawal point, and a device for providing a twist arranged between the withdrawal point and the withdrawal device, it is provided that the withdrawal device and the device for providing the twist are arranged in such a manner that the withdrawal direction corresponds essentially to the moving direction which the collecting device has in the area of the withdrawal point.
In an advantageous embodiment, it is provided that the collecting device is an axially perforated disk to which a suction device is assigned which is arranged on the side facing away from the feeding and opening device and which has a suction slot tapering from the area of the feeding point to the withdrawal point. In combination with centrifugal forces affecting the fibers, this suction slot causes a bundling of the fibers to a fiber composite.
In a further development of the invention, it is provided that a pressure roller is arranged at the withdrawal point and forms a clamping point with the disk. This pressure roller first has the task of defining the withdrawal point as precisely as possible. When its clamping effect is adjusted to be only slight, the twist given to the withdrawn fiber composite extends back against the withdrawal direction to beyond the withdrawal point in the sliver so that a truly twisted yarn is spun. When, on the other hand, a relatively strong clamping is provided between the pressure roller and the disk, a travelling-back of the twist provided to the sliver in the area of the withdrawal point is largely prevented so that then the device for providing the twist in the withdrawn yarn composite produces only a false twist; that is, a false-twist-spun yarn is produced.
In a further development of the invention, it is provided that the suction slot is extended beyond the withdrawal point. This measure has increased significance particularly if a false-twist spinning is carried out. As a result, it will therefore be possible to spread away, in the area of the extension of the suction slot, fiber ends from the fiber composite which will then result in an improved winding-around.
In a further development of the invention, it is provided that the disk is provided with an essentially axially directed border forming a collecting groove. This collecting groove has the purpose of promoting the bundling of the sliver in a defined area. In this case, it may then be expedient to throttle the suction in front of the withdrawal point or to eliminate it completely. This may, for example, be achieved by the fact that the suction slot changes already in front of the withdrawal point or that the area of the withdrawal point is subjected to a reduced vacuum.
In a further development of the invention, it is provided that a roller, which is subjected to suction and forms a yarn deflection, is arranged between the withdrawal point and the device for providing the twist. This roller is driven to a circumferential speed which is higher than the withdrawal speed. This development is particularly advantageous if a false-twist spinning is carried out. The suction roller has the effect that, at first, some edge fibers are still spread away which are then taken along by the roller, which is subjected to suction, at an increased speed so that then the edge fibers are wound in a defined manner around the fiber composite which rotates as the result of having received a twist.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.